The present invention is a new class of olefin polymerization catalysts, and methods of making the same. These new catalysts are characterized in that they are comprised of Zwitterions with significant dipole moments. Active site ion pairs are thus optimally formed of component ionic (one anionic and one cationic) moieties from different (Zwitteonic) molecules. During polymerizations that occur in nonpolar media the active species (i.e. ion pairs) become uniformly dispersed inside the polymer particles formed, while the length of the spacers separating the positive from the negative end of every Zwitterion increase as a consequence of the polymerization on the active metal-carbon bond of the catalyst.
Metallocene catalysis is a relatively new field in the art of olefinic polymerization and provides homogeneous catalysts promoting ethylene polymerization as well as xcex1-olefin polymerization to polymers of controlled structure (e.g. isotactic or syndiotactic polypropylene).
Traditional metallocene catalysts, as well as their manufacture are illustrated in the following prior art documents, which prior art documents are hereby incorporated by reference:
U.S. Pat. No. 4,542,199 describes the use of dihalo- and hydrocarbyl, halometallocenes with alumoxanes. U.S. Pat. No. 4,841,004 discloses a specific type of substituted metallocene to give 1-olefin stereoblock polymer. U.S. Pat. No. 5,091,352 describes various acceptable aluminum compounds suitable for use as cocatalysts with metallocenes and polymerization processes in the presence of isobutene.
U.S. Pat. No. 5,153,157 illustrates how the prior art references comprise a large non-limiting list of acceptable metallocene compounds which function in 1-olefin polymerization as well as the general use of large non-coordinating anionic cocatalytic components which is generally acknowledged to be one essential role of the alumoxane cocatalyst. U.S. Pat. No. 5,416,179 describes at least one non-alumoxane cocatalyst and a process for the polymerization of mono-1-olefins with metallocenes. U.S. Pat. No. 5,480,848 describes metallocene cocatalyst compositions containing acidic hydrogen free boron compounds with organoaluminoxy compounds.
One of the earliest descriptions of the metallocene methyl alumoxane (MAO) catalysts is found in the book xe2x80x9cTransition Metal Catalyzed Polymerizations Alkenes and Dienes Part Axe2x80x9d edited by Roderic P. Quirk et al., published for MNI Press by Harwood Academic Publishers, Chur, London, New York, specifically, an article entitled xe2x80x9cPolymerization and Copolymerization with a Highly Active, Soluble Ziegler-Natta Catalystxe2x80x9d by Walter Kaminsky which begins on page 225 therein.
Prior art metallocene catalysts are either unsupported or supported The former catalysts are generally soluble in the reaction media of choice and lead to small polymer particles with uncontrolled morphologies. This is a limitation which makes polymer disengagement from the reaction medium more difficult than the previous generation of olefin polymerization catalysts which are the current norm. Other aspects of downstream processing are also more difficult.
Supporting metallocene catalysts overcome some of these process limitations, but introduce other complicating factors, such as the introduction of the supporting material which dilutes the active species and contributes potentially deleterious impurities to the final polymer. The supporting process may also perturb the active catalyst species, possibly reducing activity or altering the micro-structure of the polymer produce.
Therefore, it is the objective of the present invention to provide a catalyst promoting polymerization of ethylene and alpha olefins to isotactic, syndiotactic, predominantly isotactic or predominantly syndiotactic polymers which overcomes the limitations imposed by the prior technology. The tacticity of the polymer produced depends on the structure of the transition metal containing moiety, and so other tacticities to these are also possible. Even though the catalyst is not supported, granular polymer particles which are expected to be easily separated from the reaction medium can be formed. This polymer will be absent added impurities which supported materials would have added. An added improvement would be the process simplification attendant in not needing a cocatalyst.
Another objective of the present invention is to provide methods of making the catalysts of the present invention.
A further object of the present invention is to provide a method of using the catalysts of the present invention to catalyze polymerization reactions including the catalyst material and/or xcex1-olefins.
The present invention relates to novel high dipole moment Zwitterionic metallocene catalysts which form by isomerization of an initially formed ionic metallocene catalyst. These catalysts comprise, an ionic pair shown below as (I). With the exception of the RI, group (shown in I below), formula I is similar to known catalysts. The RI group is not expected to interfere with catalyst activity other than allowing an isomerizing olefin insertion onto the metal carbon bond. Because of this isomerization the specific zwitterionic compounds of this invention are formed. Thus, these catalysts are shown in the following formula (I) and via the above noted isomerization are derived from one or more ionic pairs having the following formulae:
[(X)xMR3xe2x88x92x]+xe2x88x92[(XI)wxe2x80x94Bxe2x80x94[(XII)yxe2x80x94(CnHm)xe2x80x94RI)]4xe2x88x92w]xe2x80x83xe2x80x83(I)
wherein,
[(X)xMR3xe2x88x92x]+ designates any of the innumerable metallocene derived cationic active sites many examples of which can be found in the patents and literature generally and as cited above.
In these compounds X designates an organic moiety which contains a cyclopentadienyl, substituted cyclopentadienyl or other structure, as is commonly known in the art, which imparts the general designation xe2x80x9cmetallocenexe2x80x9d and provides the bond of the X moiety to the metal xe2x80x9cM.xe2x80x9d This moiety may be a unitary structure (x=1) in which case it may consist of, for example, one cyclopentadienyl containing structure. When x is 2, it may consist of two cyclopentadienyl or substituted cyclopentadienyl containing structures. These two cyclopentadienyl or substituted cyclopentadienyl moieties can be connected via a suitable bridge such as dimethylsilyl, diphenylsilyl, isopropylidene, 1,2ethanediyl, etc. Therefore, x is either 1 or 2 and indicates the number of expected metalcyclopentadienyl bonds.
R is a hydrocarbyl moiety. When attached to M (see below), it is preferably methyl. M is a metal usually selected from Ti, its congeners in Group IVB and the metals in the periodic table close to it including Group VB and VIB metals. Preferably, M is a transition Group IVB metal and most preferably Zr.
The xe2x88x92[(XI)wxe2x80x94Bxe2x80x94[(XII)yxe2x80x94(CnHm)xe2x80x94RI)4xe2x88x92w]] substructure represents a subset of all possibilities which define the unique portion of what has been found and described herein RI,is a terminal olefinic moiety. When n is not equal to 0 and m is not equal to 0 minimally it is xe2x80x94CHxe2x95x90CH2 or if n=m=0 minimally it is xe2x80x94CH2xe2x80x94CHxe2x95x90CH2.
B is selected from Group IIIA, and is preferably Boron.
XI is a large electron withdrawing group, as is known in the art, preferably pentafluorophenyl (C6F5). The RI moiety is connected to boron optionally through XII which is a proper spacer, for example O or NR (R as above).
CnHmis a connecting hydrocarbyl moiety with a and m chosen within the laws of valency, n is xe2x89xa70. If n=0, then m=0. Otherwise mxe2x89xa70. For purposes of economy from here on the (CnHm) moiety win be abbreviated xe2x80x9cCH.xe2x80x9d
Additionally, w is 2 or 3 and y is 0 or 1.
The ionic pairs of the present invention are capable of reacting with the unsaturations of RI that is converted to RII (see below). Due to their high dipole moment the Zwitterionic pairs (exemplified below for the specific case where x=2, w=3 and y=1) can be self-associated potentially forming clusters or networks such as the following: 
Note that the nature of the RI moiety has been altered (indicated above by RII) during the isomerization which forms the Zwitterion due to the insertion of the olefin (RI) into the Mxe2x80x94R bond. For example, in the case of n=l1, m=2 (xe2x80x9cCHxe2x80x9dxe2x95x90CH2), with RIxe2x95x90CH2xe2x80x94CHxe2x95x90CH2 where x=2, w=3, and y=1. The isomerization is as shown in (III). 
The olefinic RI was xe2x80x94CH2xe2x80x94CHxe2x95x90CH2. After isomerization of the terminal olefinic moiety (insertion onto Mxe2x80x94R) it has become RII which is 
where the open valences (*) are now connected to R and M.
The selection of the connection between RI and B can influence the dipole moment of the isomerized compound. In cases where the geometry and stiffness of the bridge inhibit intramolecular charge attraction, high dipole moments are expected.
The above chain or cluster (II) is characterized in that every cation is covalently bonded to one anion, which is not its counterion, through the xe2x80x94XIIxe2x80x94CHxe2x80x94Rf(I)xe2x80x94 bridge. Though not shown above, a branched structure is also possible After the ionic pairs are associated the active sites are situated inside their own network or cluster. The intermolecular association is forced and required by the high dipole moment of each Zwitterionic molecule which in turn derives from the nature of the moiety bridging the boron atom and the RII group (i.e. xe2x80x94(XII)yxe2x80x94(CnHm)xe2x80x94 in the previous formula and abbreviated xe2x80x94XIIxe2x80x94CHxe2x80x94 above).
Olefin polymerization occurs via monomer insertion at the Mxe2x80x94RII bond. As a result, the length of the bridge increases as the polymerization process proceeds. The ionic pairs are separated increasingly as the polyolefin is produced. Thus in the case of ethylene polymerization the xe2x80x94(XII)yxe2x80x94(CnHm)xe2x80x94RII(R) bridging moiety after j turnovers and before any chain termination reactions becomes xe2x80x94(XII)yxe2x80x94(CnHm)xe2x80x94RII(R)xe2x80x94(CH2xe2x80x94CH2)jxe2x80x94 wherein j ethylene molecules have become inserted into the Mxe2x80x94RII bond.
As the polymerization process begins, the close proximity of the ionic pairs promotes crystallization of the polymer chains. Then, as the ionic pairs are moved away from one another the catalytic sites become uniformly dispersed throughout the polymer matrix. This creates a pseudo-homogeneous catalyst by the end of the polymerization process.
One advantage of the above covalent/ionic bonded cyst is a resulting clustering of the polymer chains in the initial stages of polymerization with olefins. This creates the resultant granular polymer particles. Subsequent dispersion of the active sites during the intermediate propagation steps results in active sites randomly and homogeneously dispersed in formed polymer. This allows rapid diffusion of the monomer to the catalytic sites and avoids or reduces diffusion limitations on reaction rate and/or specificity as experienced in polyolefin processes catalyzed by supported catalysts.
As can be seen from the above, the present invention is characterized by an active catalyst comprising the structure:
[DM+xe2x80x94Axe2x80x94Exe2x88x92]xxe2x80x83xe2x80x83(IV)
wherein,
x is minimally 1. D designates any one of the possible metallocene sub-structures known in the art which are connected to the catalyst metal M. Preferably, D is a mono-, or di-. cyclopentadienyl or substituted cyclopentadienyl structure, bridged or unbridged through a connecting group.
M is selected from any one of the known metallocene transition metals, as described above. M is preferable selected from Group IVB, VB, and VIB. More preferably, M is a Group IVB metal. Most preferably, Zr or Ti. Note that the DM- structure is that of a typical metallocene catalyst as is known in the art.
A designates a connecting group comprising a hydrocarbyl containing structure, optionally containing a heteroatom structure.
E designates a large non-coordinating anion bonded through A to M. The structure of E is as is known in the art. Note that the structure of connecting group A is such that E is inhibited from acting as a coordinating anion for the metal M it is bridged to, and vice versa However, both M and E can, and preferably do, weakly coordinate with other oppositely charged moieties: E and M in other molecules.
Illustrative, but not limiting examples of possible non-coordinating anions (E) and metals (M) are shown in U.S. Pat. No. 5,153,157.
The catalyst is characterized in that olefinic polymerization is possible at the active metal site. Olefin insertion occurs at the M+xe2x80x94A bond Thus, as polymerization proceeds, the distance between M and E increases.
It should be noted that in the above structure, polymerization is possible with the E or A of another structure if that E or A contains olefinic unsaturation.
Another way of characterizing the catalysts of the present invention is that they comprise ionic pairs (the active sites), wham each of the ion constituents of each pair is covalently bonded to:an ion of the opposite charge of another ion pair. This type of bonding can result in a network among the active species. The active sites are more or less homogeneously dispersed within the catalyst network.
In one embodiment of the present invention, the ionic pairs are self-associated. The self-associated network then serves as the catalyst for polymerizing xcex1-olefin or co-polymerizing two or more olefins. In a preferred embodiment, the catalyst is utilized in propylene polymerization or ethylene-propylene co-polymerization processes.
There are several ways to obtain the active catalyst structure [DM+xe2x80x94Axe2x80x94Exe2x88x92]x. The starting materials must contain olefinic unsaturation covalently bonded to either the transition metal, or more commonly, to the cationizing compound which is preferably a boron compound. If neutral compounds are combined, a sufficiently strong Lewis acid is employed to abstract an alkyl group from the metallocene metal. This process generates an anion at the former Lewis acid site and a cation at the transition metal shown below in (V):
D(R) Mxe2x80x94R+exe2x88x92a=xe2x86x92DRM+xe2x88x92ea=xe2x80x83xe2x80x83(v)
Alternatively, a salt may be reacted with a neutral dialkyl oranometallic compound if the cationic portion of the salt is capable of de-alkyklating the alkyl metallocene. This is shown in part in (VI) below:
xe2x80x83D(R) Mxe2x80x94R+H+xe2x88x92[Exe2x88x92a=]xe2x86x92DRM+xe2x88x92[Ea=]+Rxe2x80x94Hxe2x80x83xe2x80x83(VI)
Wherein xe2x80x9cexe2x80x9d is a neutral precursor of the required anion. For example, if E is [xe2x80x94CH2xe2x80x94B(C6F5)3]xe2x88x92 then e is B((C6F5)3, and xe2x80x9ca=xe2x80x9d is the incipient bridging group xe2x80x9cAxe2x80x9d. For example, if Axe2x95x90xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94 then a= is CH2xe2x95x90CHxe2x80x94.
If a halo alkylmetallocene is used, a metal salt of the anion can be used in a transmetallation reaction analogous to the above reaction.
Once the initially formed complex:
[D(R)M]+xe2x88x92[Exe2x88x92a]xe2x80x83xe2x80x83(VII)
is obtained because of the Mxe2x80x94R bond in the cation and the CH12xe2x95x90CHxe2x80x94 group in a= an isomerization produces the Zwitterionic polymerization catalyst which can be used immediately (even the initially formed complex may be used as the isomerization will proceed under olefin polymerization conditions), stored or even physically shaped or processed to affect ultimate polymer particle morphology. The isomerization involves insertion of the unsaturation in a= onto the Mxe2x80x94R bond. The removal of the unsaturation converts a= to A.
The ultimate bridging group A may even be initially connected to the transition metal, as a=, as shown below in (VIII and IX).
DMa2=+exe2x86x92[D(a=)M]+xe2x88x92[Exe2x88x92a=]xe2x80x83xe2x80x83(VIII)
For example, if a= is xe2x80x94(CH2)nxe2x80x94CHxe2x95x90CH2 and e is B (C6F5)3, the reaction would be as follows:
DM(xe2x80x94CH2)nxe2x80x94CHxe2x95x90CH2)2+B(C6F5)3xe2x86x92[D(CH2xe2x95x90CHxe2x80x94(CH2)nM]+xe2x88x92[CH2xe2x95x90CHxe2x80x94(CH2)nxe2x80x94B(C6F5)3]xe2x80x83xe2x80x83(IX)
and the isomerization would be as follows: 
wherein,
a= is + (CH2)nxe2x80x94CHxe2x95x90CH2
nxe2x89xa71
e is B(C6F5)3 
It should be noted that the residual unsaturation in the bridging group is available for further reaction.
In another embodiment of the present invention, the catalyst is made by combining the compound X2MR2 (symbols as defined above) with a complex acid resulting from the reaction of one terminally unsaturated molecule, having an acidic xe2x80x94OH functionality, with tris(pentafluorophenyl) boron. Examples of such molecules include:
H2Cxe2x95x90CHxe2x80x94(CnHm)xe2x80x94(C6H4)OH
H2Cxe2x95x90CHxe2x80x94(CnHm)xe2x80x94SiR(I)2OH
H2Cxe2x95x90CHxe2x80x94(CnHm)xe2x80x94BR(I)OH
xcex1-alkenyl-xcfx89-fluoroalcohols (terminal or pendant xe2x80x94CF2OH groups), and
xcex1-alkenyl-xcfx89-fluorophenols (terminal or pendant xe2x80x94(C6P4)xe2x80x94OH groups)
wherein,
each R(I) is R or RI (alkenyl or substituted alkenyl group) as noted above, and
each xe2x80x94(CnHm)xe2x80x94comprises a divalent hydrocarbyl connecting group.
In another embodiment of the invention, the organometallic catalysts of the present invention are prepared by; reacting an alkali metal salt, such as lithium, of the non-coordinating anion with X2M(Hal)R, wherein Hal is F, CL Br, or I.
In another embodiment of the invention, the organometallic catalysts of the present invention are prepared by reacting the compound X2MR2 with Broensted acidic compound affording noncoordinating anions bearing at least one terminal olefinic unsaturation, such as [C6H5N(CH3)2H]+xe2x88x92[(C6F5)3B((CH2)6xe2x80x94CHxe2x95x90CH2)].
In another embodiment of the invention, the organometallic catalysts of the present invention are prepared by reacting the compound X2MR2 wit a carbenium salt of an acid affording a non-coordinating anion bearing at least one terminal olefinic unsaturation, such as triphenylmethyl tris(pentafluorophenyl) 4(1,5-hexadien-1-yl)phenyl borate ([(C6H5)3C]+xe2x88x92[(C6F5)3BC6H4xe2x80x94(CHxe2x95x90CHxe2x80x94(CH2)2xe2x80x94CHxe2x95x90CH2)]) triphenylmethyl tris(pentafluorophenyl)oct-1-enyl borate ([(C6H5)3C]+xe2x88x92[(C6F5)3B((CH2)6xe2x80x94CHxe2x95x90CH2)]) or tropylium tris(pentafluorophenyl)oct-1-enyl borate ([(C7H7]+xe2x88x92[(C6F5)3B((CH2)6xe2x80x94CHxe2x95x90CH2)]).
In another embodiment of the invention, the organometallic catalysts of the present invention are prepared by reacting the compound X2MR2 wherein both of the R groups bear at least one terminal olefinic unsaturation, in effect being better represented in the formalism above as X2MRI2, with a cation compound which abstracts Rxe2x88x92 (or better RIxe2x88x92) from X2MRI2 for example by reacting X2M((CH2)6xe2x80x94CHxe2x95x90CH2)2 with (C6F5)3B. These X2MRI2 compounds can be prepared in situ by reacting the corresponding halides (X2M)(Hal)2) with AlRI3 where the molar ratio of Al to M is equal to or larger than 2.
In another embodiment of the invention, the organometallic catalysts of the present invention are prepared by reacting the compound X2MR2 with a cationizing compound bearing at least one substitutent with a terminal olefinic unsaturation, that is B(C6F5)2[C8F4(CH2xe2x80x94CH2xe2x80x94CGxe2x95x90CH)].